Revealing mistake: During Quidditch tryouts, when Ron blocks the Quaffle with his head in the closeup, Ron's body disappears at the bottom of the screen below the digital editing line. (Only visible on fullscreen DVD).
Continuity mistake: After drinking the poison in Slughorn's office, Ron falls and in the overhead shots the top of his head is near the rug's edge, but in side shots his head is well below the large diamond pattern, more than a foot away from the edge.
Continuity mistake: When Harry finds Hermione crying at the bottom of the stairs, with the conjured canaries flying overhead, there are numerous leaves/debris on the lowest steps and near her feet, but in the shots looking down from the top of the stairs the area is clear. (This has nothing to do with the few leaves that blow about.)
Continuity mistake: When Dumbledore approaches Slughorn, who is disguised as a chair, both the sheer and opaque curtains' appearance changes back and forth - also note the holes or lack thereof, between Slughorn's close-ups and wideshots. (00:07:00)
Continuity mistake: Aboard the Hogwarts Express, when Luna finds Harry lying petrified on the floor and then speaks with him, the way she holds her wand and the Quibbler newspapers differs between shots. (00:27:40)
Continuity mistake: When Harry is in the diner and places the newspaper down on the table as he speaks with the waitress, it lies over the table edge (front and side edges), then doesn't, then does so again... (00:04:05)
Continuity mistake: At the Burrow, when Harry is speaking with Lupin, Tonks, and Arthur, and then when Ginny joins him on the sofa, the orange blanket lying on the sofa's arm to Harry's right moves forward, back, forward, etc. (01:15:00)
Continuity mistake: At the Three Broomsticks, when Slughorn and Harry speak, Slughorn holds a silver mug with a high foam head, but in the shot facing Harry, before Slughorn actually spills the drink the mug's foam head is gone (visible at the bottom of the screen), only to reappear when he spills it on Hermione ,whereupon the same previous angle is shown again without the foam.
Continuity mistake: When Dumbledore and Harry first arrive in front of Slughorn's temporary residence in Budleigh, Babberton, Harry's height barely even reaches Dumbledore's shoulders (likely the actor's stand-in), but in the next shot facing them Harry's height compared to Dumbledore is back to normal, level with the Headmaster's eyes. (00:05:35)
Continuity mistake: When Dumbledore brings Harry to meet Slughorn, the Daily Prophet is lying on the floor amongst debris, including the piano's hammer, which differs between shots. (00:06:50)
Continuity mistake: When Dumbledore and Harry are talking about Horcruxes, Harry's hair is nice and combed in one shot. The camera cuts to a side view and his hair is now messy.
Continuity mistake: In Fred and George's joke shop Ron asks how much something is, the twins reply 5 galleons, one of the twins (closest to Ron) is leaning against the banister then in the next shot of him he is in a different position.
Answer: Leaving an untrained young wizard, who obviously has some behavioral issues and has no idea he is magical, alone in the Muggle world would be extremely dangerous. Dumbledore does not yet know that Riddle will become evil, but like any teacher, he wants to give a troubled youth an opportunity to find a new path in life.
raywest ★